Robust Turn Structures in α3β Cyclic Tetrapeptides Induced and Controlled by Carbo-β3 Amino Acid
摘要:
Designing cyclic tetrapeptides (CTPs), which fold into desired structures, is often a challenging task. While it is difficult to synthesize them, they are also prone to adopt multiple conformations. In this paper we report the synthesis and conformational studies of CTP mimics, having nonconstrained alpha(3)beta motif, that exhibit stable beta- and gamma-turn structures. We also demonstrate the transformation of beta-turn to gamma-turn structure in similar CTPs by inverting the chirality of beta carbon in C-linked-carbo-beta(3)-amino acid (Caa) from R to S.
Asymmetric organocatalysis with glycosyl-β-amino acids: direct asymmetric aldol reaction of acetone with aldehydes
作者:Namrata Dwivedi、Surendra S. Bisht、Rama P. Tripathi
DOI:10.1016/j.carres.2006.08.007
日期:2006.11
Directasymmetricaldolreaction of acetone with aromatic aldehydes was achieved in good yields and high enantioselectivity using 5-amino-5-deoxy-beta-L-ido-(alpha-D-gluco)-heptofuranuronic acids as a new class of organocatalysts.
Investigation and folding pattern of l-ido and d-gluco peptides by EASY ROESY NMR and X-ray
作者:Sachin A. Pawar、Amit M. Jabgunde、Katja Petzold、Glenn E. M. Maguire、Dilip D. Dhavale、Hendrik G. Kruger、Thavendran Govender
DOI:10.1039/c3ra44542a
日期:——
The sugar β-amino acid plays an important role in the formation of well-defined secondary structures of peptides. The combination of change in the functional group, stereocenter on the sugar amino acid and peptide attachment to the glycopeptide revealed important information about their secondary structure. The stereocentre (C5–H) of the sugar β-amino acid in these peptidic diastereomers controls the folding behaviour of these compounds. Conformations of the considered compounds were established by NMR (EASY-ROESY) and compared with the 3D structure obtained from X-ray crystallography.
糖 β-氨基酸在形成定义明确的肽二级结构中起着重要作用。糖氨基酸上的官能团、立体中心和肽附着在糖肽上的变化相结合,揭示了其二级结构的重要信息。这些肽非对映异构体中β-氨基酸糖的立体中心(C5-H)控制着这些化合物的折叠行为。通过核磁共振(EASY-ROESY)确定了所研究化合物的构象,并与 X 射线晶体学获得的三维结构进行了比较。
One-Pot Synthesis of Glycosyl-β-azido Ester via Diazotransfer Reaction Toward Access of Glycosyl-β-triazolyl Ester
作者:Amrita Mishra、Vinod K. Tiwari
DOI:10.1021/acs.joc.5b00179
日期:2015.5.15
A concise and efficacious one-pot protocol for the synthesis of novel glycosyl-beta-azido ester 3 from glycosyl olefinic ester 1 under mild conditions has been devised. The beta-aminoester, formed by the conjugate addition of ammonia on olefinic ester, undergoes a metal-catalyzed diazotransfer reaction to furnish glycosyl-beta-azido ester. The optimized conditions for diazotransfer reaction indicate that imidazole-1-sulphonyl azide and K2CO3 give the best results in the presence of ZnCl2. A diverse range of novel regioselective triazolyl glycoconjugates 6a-u have been achieved in high yields via 1,3-dipolar cycloaddition of compound 3 with various alkynes in the presence of Cul/DIPEA. Structures of all the compounds have been elucidated using IR, NMR, MS, and elemental analysis, and four of them (3a, 3b, 4b, and 6a) have also been characterized by single crystal X-ray diffraction analysis.
Synthesis of glycosylated β-amino acids as new class of antitubercular agents
A series of glycosylated P-amino acids was prepared and evaluated against Mycohacterium tuberculosis, M. avium, M. fortuitum and M. smegmatis. The compounds were designed to mimic the enzyme D-alanine racemase and glycosyl transferase involved in the biosynthesis of essential cell wall peptidoglycan and arabinogalactan. Though most of the compounds exhibited little activity, however, one showed significant activity against all the strains in cell culture and activity was confirmed by BACTEC method. (C) 2002 Editions scientifiques et medicales Elsevier SAS. All rights reserved.
A Versatile Synthesis of Dihydropyrimidinone<i>C</i>‐Nucleosides
作者:Ram Chandra Mishra、Diksha Katiyar、Neetu Tewari、Rama Pati Tripathi
DOI:10.1081/ncn-120030712
日期:2004.12.31
A versatile synthesis of N-substituted dihydropyrimidinone C-nucleosides (20-29) is described. Glycosyl amino esters (3-9), obtained by reductive alkylation of glycosyl amino esters 1 and 2, on condensation with different isocyanates afforded respective ureido derivatives (10-19) in good to quantitative yields. The latter on cyclative amidation with a combination of DBU/TBAB (tetrabutylammonium bromide)/4Angstrom molecular sieve gave the corresponding nucleosides (20-29) in good yields.